Friday, January 05, 2007

Non-identical and Identical Identicals

In preparing our new site I got sidetracked looking at twin data. As a gay man and a father of fraternal twins, it interests me (and some of the numbers are just funny). The following data, if a single percentile, are hereditability figures. Thus 100% would mean the trait is completely genetically hereditable. Some other data below comes in concordance form and so the identical twin concordance (siblings with the same genes ) is first and the fraternal twin (siblings with different genes) is second. Thus, if the identical twin’s concordance is 100% and the fraternal is 0% one could near safely say genetics is the cause of the trait.

Eye color: 87% (1)It surprised me this isn’t nearer 100%. I mean, I was under the impression, if it's not genetic, then it's a choice... ;-) Why are people choosing their eye color to be different from their twin?Crypts in eye: 75% (1)Those are specks in your brother’s eye…

Height: 88% (2)Weight: 88% (2)

Left Handedness: 15% vs. 9% (3) (concordance)See this post for more on handedness , or about my disdain for those who practice such a lifestyle here.

Onset of Puberty: 50-80% (4)The important trigger to most of our realizations and experiences of our sexual orientations, gay or straight.

Opinion and Personality:All the following are from reference 8, and all are concordance numbers for identical vs fraternal twins. Also, I’ve just picked the interesting ones out and there are more if if you’d like to look at the paper.

Political and Social attitude in all: 36% (8) hereditability when all opinions are averaged.Political and Social attitude in all from a different, repeat study: 18-41% (9) (depending on the particular issue from abortion to immigration)Being a Republican: 36% :-) (9)A Socialist: 36%Isn’t that a pretty big hereditability for something we take as stridently as politics :-)?

And finally:Gay Rights: 28% genetic hereditability in opinion on gay rights. LOL, Some just can’t help being queer lovers or homophobes; they’re born that way :-).